The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Ionized gas, or plasma, is commonly used during the processing and fabrication of semiconductor devices. For example, plasma can be used to etch or remove material from a substrate such as a semiconductor wafer, and to sputter or deposit material onto the substrate. Creating plasma for use in manufacturing or fabrication processes typically begins by introducing process gases into a processing chamber. The substrate is disposed in the processing chamber on a substrate support such as an electrostatic chuck or a pedestal.
The processing chamber may include a transformer coupled plasma (TCP) coil. A radio frequency (RF) signal, supplied by a power supply, is supplied to the TCP coil. A dielectric window, constructed of a material such as ceramic, is incorporated into an upper surface of the processing chamber. The dielectric window allows the RF signal from the TCP coil to be transmitted into the interior of the processing chamber. The RF signal excites gas molecules within the processing chamber to generate plasma.
A bias RF power source supplies a biasing RF signal to the substrate support. The biasing RF signal can be used to increase the direct current (DC) bias and/or a DC sheath potential to increase the energy with which the charged particles strike the substrate. Variations in the biasing RF signal produce corresponding variations in the DC bias and/or DC sheath potential at the substrate affecting the process characteristics.
A pickup device may be attached to the substrate support and is used to detect an RF input signal at the substrate support. A RF detector is connected to the pickup device and detects the RF input signal. The biasing RF signal may be adjusted based on the detected RF input signal, for example, to minimize variations in the DC bias and/or the DC sheath potential at the substrate.